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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 5 (1985), S. 103-122 
    ISSN: 0886-1544
    Keywords: gliding ; cell motility ; cytoskeleton ; diatoms ; capping ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gliding motility was investigated in the marine diatom, Amphora coffeaeformis. Ultrastructural, biochemical, and pharmacological protocols were employed to probe the possible involvement of cytoskeletal proteins and a secretory process in gliding motility. Motility rate was measured using a video recording apparatus, and the effects of various cytoskeleton-disrupting drugs on motility were tested. Cytochalasins D and E, podophyllotoxin, and vinblastine (all at 25 μUg/ml) reversibly inhibited motility, as did monensin (10 μUM) and pronase (25 μUg/ml). Biochemical protein analysis of whole-cell extracts by one- and two-dimensional polyacrylamide gel electrophoresis revealed polypeptides comigrating with rabbit skeletal muscle actin and bovine brain tubulin; however, specific assays used to separate actin from whole-cell preparations gave ambiguous results. Ultrastructural studies revealed the presence of extracellular material between the raphe canal and the substratum in motile cultures. An assay was devised for the detection of radioactively labeled material (MW 〉 1800 Daltons) released by motile cultures into the culture medium. When cultures were treated with either an anticytoskeletal drug or monensin, motility was inhibited while the amount of measured radioactivity increased over solvent-treated control groups. The results from this study indicate possible roles for both actin- and tubulin-based structures in gliding motility of Amphora. Though secretion may be necessary for gliding to occur, its exact relationship to motility was not deduced. The data obtained in this study are compatible with a theory for the mechanism of gliding which involves the surface translocation of externally exposed membrane proteins against an immobile matrix of substratum-attached secreted material to generate the force required for movement.
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Retinoids are currently being tested for the treatment and prevention of several human cancers, including breast cancer. However, the anti-cancer and growth inhibitory mechanisms of retinoids are not well understood. All-trans retinoic acid (RA) inhibits the growth of the estrogen receptor-positive (ER+) breast cancer cell line, MCF-7, in a reversible and dose-dependent manner. In contrast, insulin-like growth factors (IGF-I,IGF-II) and insulin are potent stimulators of the proliferation of MCF-7 and several other breast cancer cell lines. Pharmacologic doses of RA (≤10-6M) completely inhibit IGF-I-stimulated MCF-7 cell growth. Published data suggest that the growth inhibitory action of RA on IGF-stimulated cell growth is linear and dose-dependent, similar to RA inhibition of unstimulated or estradiol-stimulated MCF-7 cell growth. Surprisingly, we have found that IGF-I or insulin-stimulated cell growth is increased to a maximum of 132% and 127%, respectively, by cotreatment with 10-7 M RA, and that 10-9-10-7 M RA increase cell proliferation compared to IGF-I or insulin alone. MCF-7 cells that stably overexpress IGF-II are also resistant to the growth inhibitory effects of 10-9-10-7 M RA. Treatment with the IGF-I receptor blocking antibody, αIR-3, restores RA-induced growth inhibition of IGF-I-treated or IGF-II-overexpressing MCF-7 cells, indicating that the IGF-I receptor is mediating these effects. IGFs cannot reverse all RA effects since the altered cell culture morphology of RA-treated cells is similar in growth-inhibited cultures and in IGF-II expressing clones that are resistant to RA-induced growth inhibition. These results indicate that RA action on MCF-7 cells is biphasic in the presence of IGF-I or insulin with 10-9-10-7 M RA enhancing cell proliferation and ≥ 10-6M RA causing growth inhibition. As IGF-I and IGF-II ligands are frequently detectable in breast tumor tissues, their potential for modulation of RA effects should be considered when evaluating retinoids for use in in vivo experimental studies and for clinical purposes. Additionally, the therapeutic use of inhibitors of IGF action in combination with RA is suggested by these studies. © 1995 Wiley-Liss Inc.
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The interaction of insulin-like growth factors (IGFs) with the IGF-1 receptor is an important step in the control of cell proliferation and development. In particular, IGF-1 and IGF-2 are key regulators of central nervous system development, and may modulate the growth of glial tumors. We have investigated the growth factor regulation of the human glioblastoma cell line T98G. These cells growth arrested in serum-free medium at 34°C, despite their secretion of substantial amounts of bioactive IGF-1. To be stimulated to divide, growth-arrested cells required the addition of platelet-derived growth factor (PDGF) or its equivalent, 1% serum. Cell proliferation in serum-free medium could also be obtained by shifting the cells to a temperature of 39.6°C. Treatment of growth-arrested cells with PDGF or temperature shift was accompanied by a transient increase in the expression of the mRNA for the IGF-1 receptor. Transfection with a plasmid constitutively expressing the full cDNA for the human IGF-1 receptor allowed autonomous growth in serum-free medium at 34°C. By contrast, growth induction by growth factors or temperature shift was abrogated by transfection of the cells with a plasmid expressing a 300 bp segment of mRNA antisense to the IGF-1 receptor mRNA. Cloning in soft agar was also inhibited by expression of antisense IGF-1 receptor mRNA. These results demonstrate that the IGF-1 receptor is strictly required for the growth of T98G glioblastoma cells. Moreover, the autocrine interaction of IGF-1 with its receptor regulates both autonomous and anchorage-independent growth of these cells. © 1994 wiley-Liss, Inc.
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional polypeptide which acts as mitogen, motogen, or morphogen. In this study, we examined the effect of HGF/SF on human hair growth using organ and cell culture systems. HGF/SF was found to stimulate hair length and DNA synthesis in hair follicles at increasing concentrations up to 10 ng/ml (P 〈 0.05 and P 〈 0.01, respectively). HGF/SF stimulated [3H]thymidine incorporation by hair bulb-derived keratinocytes with the strongest response at 30 ng/ml of HGF/SF (P 〈 0.05). Cultured follicular papilla cells secreted HGF/SF, measured by an enzyme-linked immunoassay, in response to interleukin 1-α (IL1-α, 10 ng/ml), tumor necrosis factor-α (TNF-α, 10 ng/ml), or tetradecanoylphorbolacetate (100 nM) at levels ranging from 0.2 to 0.3 ng/mg protein/48 h. HGF/SF mRNA expressions, measured by the reverse transcription-polymerase chain reaction, were detected in follicular papilla cells, and were also stimulated by the three reagents. Transforming growth factor-β (10 ng/ml) suppressed both protein and mRNA levels. These results suggest that hair follicle elongation induced by HGF/SF in organ culture occurs partly due to the mitogenic activity of HGF/SF expressed in follicular papilla cells on hair bulb-derived keratinocytes. © 1995 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 272-283 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The maintenance of the normal epithelioid morphology of human dermal microvascular endothelial cells (MEC) grown in vitro depends strongly on the presence of factors that increase intracellular levels of cyclic AMP. Complete removal of dibutyryl cAMP and isobutylmethyixanthine (IMX) from the growth medium results in a progressive transition from an epithelioid to a spindle-shaped cell line. This transition cannot be reversed by the readdition of dibutyryl cAMP and IMX to the growth medium or by addition of agonists that increase cAMP levels. Spindle-shaped MEC lose the ability to express Factor VIII rAG and DR antigens and to bind peripheral blood mononuclear leukocyte (PBML).Ultrastructural analyses of transitional cells and spindle-shaped cells show decreased numbers of Weibel-Palade bodies in transitional cells and their complete absence in spindle-shaped cells. Interferon-γ alters several functional properties of both epitheliod and spindle-shaped cells. In the absence of dibutyryl cAMP it accelerates the transition from epithelial to spindle-shaped cells, whereas in the presence of cyclic AMP interferon-γ increases the binding of PBMLs to both epithelioid and spindle-shaped MEC and the endocytic activity of the endothelial cells.These results suggest that cyclic AMP is an important second messenger in the maintenance of several key functions of microvascular endothelial cells. Factors that influence the levels of this messenger in vivo can be expected to influence the angiogenic and immunologic functions of the microvasculature.
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  • 6
    Electronic Resource
    Electronic Resource
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 64 (1964), S. 173-179 
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Rous sarcoma virus (RSV) is unique among tumor viruses in the great speed and high frequency with which it induces the malignant transformation in the infected cell. It is also unique in its defectiveness  -  it cannot reproduce new, infectious virus particles unless a helper virus is present. Such a helper virus, known as RAV, occurs in stocks of the Bryan high titer strain of RSV. It is a member of the avian leukosis group of viruses. All the other avian leukosis viruses tested to date can substitute for RAV as helper viruses. An analysis has been carried out of the independent and helper-dependent functions of RSV. RSV carries out the malignant transformation of cells without the aid of helper virus and controls the morphology of the transformation. It also reproduces its own genetic material in solitary infection. However, it is completely dependent on helper virus for synthesis of its protein coat. As a result, RSV bears the antigenic identity of its helper virus. By using different helper viruses, it has been found that the ability of RSV to infect chicken cells of a given genetic constitution depends on the coat of the virus. In addition, the susceptibility of RSV to interference by leukosis viruses depends on similarity between the coat of the leukosis virus and that of the super-infecting RSV. The results to date indicate both these forms of cellular resistance to RSV are associated with the failure of RSV to penetrate the cell.
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  • 7
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Tab.
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  • 8
    ISSN: 0730-2312
    Keywords: extracellular matrices (ECMs) ; bFGF ; NGF ; HGF and KGF ; growth factors (GFs) ; human prostate cancer model ; prostate cancer-bone interaction ; stromal-epithelial interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A human prostate cancer model was established by inoculating a prostate specific antigen (PSA)-producing LNCaP cell line with either prostate or bone fibroblasts. Alternatively, this human prostate cancer model can also be established by inoculating LNCaP cell with growth factor(s) (GFs) and extracellular matrix (ECM) immobilized on Gelfoam®. The resulting LNCaP tumors were used to evaluate PSA production and excretion athymic hosts. This model was also employed to examine the biochemical nature of mesenchymal cell-derived growth-promoting protein(s) and to assess the efficacy of potential chemotherapeutic agents. Because of the propensity of human prostate cancer to metastasize to the bone, this study defined a 1.0 M NaCI-eluted fraction, MS1, from the conditioned medium of a bone stromal cell line (MS) by heparin-affinity column chromatography. The growth-promoting activity was assayed both in vivo (e.g., tumor formation) and in vitro (e.g., soft agar colony formation). We found that the growth-promoting activity was trypsin-and heat-sensitive, and partially degraded by acid and dithiothreitol. Immunochemical studies indicated that the polyclonal antibody raised against MS1 blocked the growth-promoting effect elicited by the bone-conditioned media. This growth-promoting factor was found to be immunochemically dissimilar to KGF, HGF, and bFGF. However, addition of bFGF, HGF and NGF, but not a FGF, TGFβ, IGF1, IGF2, PDGF, EGF, TGFα and KGF, stimulated anchorage-independent growth of prostate cells, a condition closely parallel to tumor formation in vivo. We found that the MS1 fraction also contained fibronectin and tenascin but not laminin or collagen IV. None of the ECM proteins induced soft agar colony formation by normal prostate epithelial cells. Therefore, it is possible that the ECM protein(s) may potentiate the tumor-inducing activity of locally produced GFs. © 1992 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 188 (1986), S. 225-238 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The iris of the toad Bufo marinus is directly photosensitive and will constrict in response to light striking only the iris. This is true even when the iris is isolated from the rest of the eye, and therefore from reflex neuronal influences initiated in the retina. This autonomous response is probably mediated by the sphincter pupillae muscle, since no specialized photoreceptors are present in the iris, nor does the sphincter exhibit any specializations likely to subserve a purely photoreceptive function. The photosensitive sphincter appears typical of smooth muscle and, like mammalian sphincters, possesses many intercellular junctions. The iris possesses a well-developed neuronal plexus with fibers projecting into the sphincter muscle layer. Nerve terminals contain small, agranular (30-70nm) and large, dense-cored (80-120nm) vesicles. No consistent postsynaptic specializations are seen on any cells of the iris, including the cells of the sphincter muscle. The anterior pigment epithelial cells of the iris appear specialized and resemble the myoepithelial dilator muscle described by Kelly and Arnold ('72) for the iris of rats.
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  • 10
    ISSN: 0730-2312
    Keywords: TGF-α ; antisense oligonucleotides ; head and neck cancer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Interruption of an autocrine growth pathway involving TGF-α and EGFR may inhibit tumor growth and improve survival in head and neck cancer patients. We previously demonstrated that biopsy specimens and established cell lines from patients with squamous cell carcinoma of the head and neck (SCCHN) overexpress TGF-α and its receptor, epidermal growth factor receptor (EGFR) at both the mRNA and protein levels. Protein localization studies showed that TGF-α and EGFR are produced by the same epithelial cells in tissues from head and neck cancer patients further supporting a role for this ligand-receptor pair in an autocrine growth pathway. To confirm that TGF-α contributes to autocrine growth, we examined the effect of down regulation of TGF-α protein on SCCHN cell proliferation. Treatment of 6 SCCHN cell lines with antisense oligodeoxynucleotides targeting the translation start site of human TGF-α mRNA decreased TGF-α protein production by up to 93% and reduced cell proliferation by a mean of 76.2% compared to a 9.7% reduction with sense oligonucleotide (range P〈0R 〉 = 0.036-0.0001). TGF-α antisense oligonucleotide exposure also decreased TGF-α protein levels in normal oropharyngeal mucosal epithelial cells, however their growth rate was not affected. These findings indicate that TGF-α is participating in an autocrine signaling pathway in transformed, but not in normal mucosal epithelial cells, that promotes proliferation. J. Cell. Biochem. 69:55-62, 1998. © 1998 Wiley-Liss, Inc.
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